In a laboratory at Delft University of Technology in the Netherlands, physicists have overturned an assumption their own theory had quietly relied on: the nucleus of a single atom, long thought to be out of reach of the electrical signals used in their instrument, responded to radio-frequency pulses and flipped its magnetic orientation. It is a small event in the long human effort to understand the hidden magnetism inside matter, yet it reminds us how often nature keeps its surprises in the places we assumed were already closed. What it might one day mean for storing quantum information remain
Delft Physicists Flip the Nuclear Spin of a Single Atom with Radio Waves, Defying Expectations
The nuclear spin should not be sensitive at all to these signals.
Mark
Why is flipping one nucleus such a big deal?
Mimi
Because the nucleus was thought to be out of reach with this instrument. Its spin is weak but well shielded from the outside world, which is exactly what you want for keeping information safe.
Mark
So the shielding cuts both ways?
Mimi
It seems so. Hard to disturb usually means hard to control, and that's why the team's result surprised them.
Luke
Let me pin down what's actually shown. They flipped the nuclear spin. Do they know how?
Mimi
No. Otte says the simple understanding says it shouldn't happen, and the work mainly raises questions about the mechanism.
Luke
Then any talk of quantum storage is a possibility, not a result.
Mimi
Right. The source says it could provide new opportunities, nothing more.
Mark
What did the two simultaneous signals add?
Mimi
They let the team study each influence independently, and the nuclear flip happened even when electron and nucleus were largely disentangled.
Luke
And the guitar comparison is Vennema's illustration, not a measurement. The only figure given is that nuclear notes are a hundred to a thousand times lower than electron ones.
El Pulso
- A working theory that physicists trusted said the nucleus of a single atom should be deaf to the signals used in their instrument, yet it responded anyway.
- The result, published in Nature Communications, caught the Delft team off guard and forced an immediate rethinking of what they thought they understood.
- Researchers sent two signals at once, one aimed at the electron and one at the nucleus, separating their influences to pin down where the surprise came from.
- The mechanism behind the flip is still unknown, so the team is back at the drawing board, with practical quantum storage applications still speculative.
In a laboratory at Delft University of Technology in the Netherlands, physicists have overturned an assumption their own theory had quietly relied on: the nucleus of a single atom, long thought to be out of reach of the electrical signals used in their instrument, responded to radio-frequency pulses and flipped its magnetic orientation. It is a small event in the long human effort to understand the hidden magnetism inside matter, yet it reminds us how often nature keeps its surprises in the places we assumed were already closed. What it might one day mean for storing quantum information remains, for now, an open question rather than a promise.
At Delft University of Technology, a team of physicists has done something their own theory insisted was impossible. Using radio-frequency signals, they flipped the magnetic orientation of the nucleus of a single atom, a feat that had been considered out of reach for the electrical signals in their instrument. The finding, published in Nature Communications, surprised the researchers themselves.
The nucleus is a weaker magnet than the electrons around it, but it is also far better shielded from the outside world, which is why it was so hard to reach. Lead researcher Sander Otte's group works with a converted scanning tunnelling microscope that can direct electrical signals at one atom with great precision. Earlier work had only sensed the nuclear spin indirectly, through its faint entanglement with the electron.
Main author Hester Vennema and her colleagues changed that approach. By sending two signals at once, one to the electron and one to the nucleus, and refining a technique called double magnetic resonance for a single atom, they could study each influence on its own. The nuclear spin flipped even when the two were largely disentangled, which should not have happened.
Vennema compares the method to a guitar, where each possible rotation is a string with its own note that only the exact frequency can set vibrating. Nuclear notes are a hundred to a thousand times lower than electron notes. Nuclear spin may one day help store quantum information securely, but for now the result mainly raises questions. As Otte puts it, it is back to the drawing board, and there is always something new left to figure out.
At Delft University of Technology in the Netherlands, a team of physicists has done something their own working theory said should not happen: they flipped the magnetic orientation of the nucleus of a single atom using radio-frequency signals. The result, published in Nature Communications, caught the researchers off guard. Until now, physicists believed this nuclear spin could not be manipulated directly with the kind of electrical signals used in their instrument.
Some background helps here. In metals such as iron and nickel, every atom is slightly magnetic. Inside each atom, though, several smaller magnetic "compass needles" are at work, which quantum mechanics calls spins. Lead researcher Sander Otte says by far the strongest magnetism comes from the electrons. In some atoms, however, the nucleus carries a spin too. It is much weaker, he says, but also much better shielded from the outside world.
Otte's group studies spins with a converted scanning tunnelling microscope, an instrument that can direct electrical signals with extreme precision at one atom. In earlier work the team concentrated on the electron spin, the easiest to read out. The nuclear spin showed up only indirectly, through what is called the hyperfine interaction, which causes the nucleus and electron spins to become slightly entangled.
The new experiment changed that. Main author Hester Vennema and her colleagues sent two different signals to an atom at the same time, one aimed at the electron and one at the nucleus, so they could study the influence of each separately. To do this, the team refined an established technique known as double magnetic resonance and adapted it for a single atom. The surprise came when they found they could flip the nuclear spin even when the two spins were largely disentangled.
Otte was direct about why that mattered. By the group's simple understanding, he says, this should not really happen: the nuclear spin should not be sensitive at all to the electrical signals from a scanning tunnelling microscope.
Vennema offers a guitar analogy for how the method works. In magnetic resonance, a wave signal changes the orientation of a spin, and quantum mechanics permits only a limited set of such rotations, so the signal must have exactly the right frequency. Each possible rotation is like a string with its own note, she explains, and only the precise note makes that string vibrate. The notes of a nuclear spin are a hundred to a thousand times lower than those of an electron spin.
The nuclear spin is of particular interest for applications where quantum information must be stored securely, and the ability to control it could open new ways of storing and reading that information. For now, though, the work mainly raises questions about what mechanism is driving the nuclear spin. "Back to the drawing board, then," Otte says, adding that this is how science works and that there is always something new left to figure out.
Citas Notables
According to our simple understanding, this should not really happen.— Sander Otte, lead researcher
Each possible spin rotation is like a guitar string with its own note; you have to play precisely the right one.— Hester Vennema, main author (paraphrased)
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